Three-dimensional ordered diamond cellular structures and method of making the same

ABSTRACT

Various implementations and embodiments relate to three-dimensional open cellular diamond micro-truss structures and methods.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a divisional of U.S. patent application Ser.No. 13/017,704, by Roper et al., entitled THREE-DIMENSIONAL ORDEREDDIAMOND CELLULAR STRUCTURES AND METHOD OF MAKING THE SAME filed Jan. 31,2011, herein incorporated by reference in its entirety.

U.S. patent application Ser. No. 13/017,704 is related to the followingU.S. patent applications, all therein and hereby incorporated byreference in their entireties:

-   -   Ser. No. 11/580,335, filed on Oct. 13, 2006 entitled OPTICALLY        ORIENTED THREE-DIMENSIONAL POLYMER MICROSTRUCTURES, by Jacobsen,        issued as U.S. Pat. No. 7,382,959 on Jun. 3, 2008;    -   Ser. No. 11/801,908, filed on May 10, 2007 entitled        THREE-DIMENSIONAL ORDERED OPEN-CELLULAR STRUCTURES, by Alan J.        Jacobsen; and William B. Barvosa-Carter, issued as U.S. Pat. No.        8,197,930 on Jun. 12, 2012;

Ser. No. 12/074,727, filed Mar. 5, 2008, entitled CERAMIC MICRO-TRUSS,by Adam F. Gross, Alan J. Jacobsen; and Robert Cumberland, issued asU.S. Pat. No. 7,687,132 on Mar. 30, 2010; and

Ser. No. 11/870,379, filed Oct. 10, 2007, entitled ORDERED OPEN-CELLULARCARBON MICRO-TRUSS STRUCTURE AND METHOD OF MAKING SAME, by Jacobsen,issued as U.S. Pat. No. 8,585,944 on Nov. 19, 2013.

BACKGROUND

As the need for high performance materials, such as those used in spaceoptics and the aerospace industry continue to expand, it has becomeincreasingly necessary to introduce new technologies to keep up withgrowing demands. Current technologies try to facilitate the need forreduced area density of space optic materials, while preserving orincreasing the stiffness.

Currently, beryllium has been used in space optics applications becauseit is known as one of the best specific stiffness materials. However,there have been disadvantages associated with the use of beryllium.Beryllium is known to be toxic and carcinogenic, with short to long termexposure, and can lead to health problems. In addition, fabrication ofstructures with beryllium can be difficult. In particular, berylliumwelding without filler material often is limited to thin foils, whichcan require high-purity, high-performance beryllium components to bemachined. For example, creating a high performance mirror from asandwich panel structure consisting of two face sheets separated by acore can be difficult when starting with solid beryllium.

Recently, there has been interest in using diamond in structures.Diamond is known to have the highest specific stiffness of any material.However, although these diamond structures exist, they are typicallyrandom diamond foams. Disadvantages with these random foam structurestypically yield mechanical, thermal and electrical properties which areinferior to materials with an ordered, rationally designed and optimized3-D microstructure.

Silicon carbide random foams have also been used, but can bedisadvantageous. Random cell foams typically have lower stiffness-tomass ratios than micro-architected ordered cellular truss materials.Additionally, silicon carbide typically can have a lowerstiffness-to-mass ratio than diamond. Furthermore, silicon carbide canalso have a higher thermal distortion parameter (ratio of coefficient ofthermal expansion to thermal conductivity) than diamond.

Therefore, while these aforementioned diamond structures can be useful,they are often disadvantageously time consuming to make, typically usingpyrolysis, sintering, gas-phase or dip coating processes, which canoften require additional steps. Furthermore, structures such as foams,are not ordered microstructures, and can suffer from randominterconnections in their forms, thereby reducing the strength of thematerials per unit weight. In addition, bulk diamond can be expensiveand may not be available in large sizes.

The use of three dimensional (3D) ordered polymer cellular micro-trussmaterials, allows fabrication of optical components with highstiffness-to-mass ratio. Additionally, lower weight is desirable foruses as aerospace components. These 3D ordered polymer cellularstructures have been created using optical interference patterntechniques, also called holographic lithography; however, structuresmade using these techniques have an ordered structure at the nanometerscale and the structures are limited to the possible interferencepatterns, as described in Campbell et al., “Fabrication Of PhotonicCrystals For The Visible Spectrum By Holographic Lithography,” NATURE,Vol. 404, Mar. 2, 2000, which is incorporated by reference herein in itsentirety.

Previous works have also been done on creating polymer opticalwaveguides. A polymer optical waveguide can be formed in certainphotopolymers that undergo a refractive index change during thepolymerization process. When a monomer that is photo-sensitive isexposed to light (e.g., UV light) under the right conditions, theinitial area of polymerization, such as a small circular area, will“trap” the light and guide it to the tip of the polymerized region dueto the index of refraction change, further advancing that polymerizedregion. If the polymer is sufficiently transparent to the wavelength oflight used to initiate polymerization, this process will continue,leading to the formation of a waveguide structure, or fiber, withapproximately the same cross-sectional dimensions along its entirelength. This phenomenon has been suggested for applications, such asfiber optic interconnects, for example. The existing techniques tocreate polymer optical waveguides have only allowed one or a fewwaveguides to be formed, and these techniques have not been used tocreate a self-supporting three-dimensional structure by patterningpolymer optical waveguides.

Inorganic polymer materials, such as pre-ceramic polymers have been usedto form ceramic micro-truss structures. These pre-ceramic polymers havebeen used to form specific polymer-based structures that can besubsequently heat treated (pyrolyzed/sintered) to create near net shapeceramic structures.

Advantages of ceramic micro-truss materials include high temperaturestability and attractive strength to weight ratios. The importance ofthese high temperature ceramic micro-truss structures makes thesestructures amenable to a wide variety of applications, such as theautomotive and aerospace industries. These ceramic micro-truss materialscould be used for lightweight, high temperature structural applicationsor for other applications that can utilize the unique porosity, such asthermal ground planes.

Therefore, it is desirable to provide diamond materials with orderedinterconnected three-dimensional ceramic microstructures that arelightweight, highly durable, hard materials, and can withstand a hightemperature environment. Furthermore, it would be advantageous to usethe minimum amount of diamond so that large-scale diamond structures canbe fabricated.

SUMMARY

In accordance with various embodiments and implementations, a method ofmaking an ordered three-dimensional open cellular diamond micro-trussstructure is provided.

In one implementation a method of forming an ordered three-dimensionalopen-cellular diamond micro-truss structure is provided which includesproviding an open-cellular polymer template and converting the polymertemplate to an open-cellular carbon micro-truss structure template. Itfurther includes depositing a film having diamond over the open-cellularcarbon micro-truss template to form a coated micro-truss diamondcomposite structure.

In various implementations, the method may further include applying adiamond-compatible coating to the open-cellular carbon micro-trussstructure template with a material to form a coated open-cellular carbonmicro-truss template and depositing the film of diamond on the coatedopen-cellular micro-truss template to form a coated micro-truss-diamondcomposite structure. The coated micro-truss diamond composite structureis etched with an effective etchant under conditions to etch thediamond-compatible coating from the coated micro-truss diamond compositestructure, to create an ordered three-dimensional open-cellular diamondmicro-truss structure.

In some implementations, the open-cellular polymer template may beformed from an interconnected pattern of self-propagating waveguides.

In various implementations, the diamond-compatible coating may be amaterial such as refractory metals, ceramics, silicon carbide, siliconnitride, hafnium carbide, chromium carbide, boron nitride, boroncarbide, aluminum oxide, titanium diboride, titanium nitride, zirconiumdioxide, titanium carbide, titanium carbonitride, tantalum carbide andtantalum nitride.

In various implementations, the film having diamond may be deposited bya gas phase deposition technique such as hot wire chemical vapordeposition (HWCVD), plasma enhanced chemical vapor deposition (PECVD),or microwave-assisted chemical vapor deposition.

In various embodiments, the deposited diamond may be monocrystalline,polycrystalline, nanocrystalline, or amorphous.

In some implementations, the effective etchant may be a molten saltselected from the group consisting of potassium hydroxide (KOH), sodiumhydroxide (NaOH), potassium nitrate (KNO₃), sodium oxide (Na₂O₂) andsodium nitrate (NaNO₃), and mixtures thereof.

In one implementation, a method of forming an ordered three-dimensionalopen cellular diamond micro-truss structure is provided which includesproviding an open-cellular polymer template, converting the polymertemplate to a vitreous carbon template, and applying a silicon carbidecoating to the vitreous carbon template to form a silicon carbidetemplate. A film having diamond is deposited on the silicon carbidetemplate to form a silicon carbide-diamond composite structure. Thesilicon carbide-diamond composite structure may be etched with aneffective etchant under conditions to etch the silicon carbide coatingto create an ordered three-dimensional diamond micro-truss structure.

In some embodiments, the three-dimensional diamond micro-truss structuremay include a network of hollow tubes made of diamond. The network ofhollow tubes may have bi-layer walls of diamond. The network of hollowtubes may further include silicon carbide.

In another embodiment of the present invention, a three-dimensionaldiamond micro-truss structure is provided. The diamond micro-trussstructure may include a three-dimensional open-cellular carbonmicro-truss structure template with a film having diamond deposited overthe micro-truss structure template to create an ordered diamondmicro-truss. The three-dimensional ordered polymer template may beformed from an interconnected pattern of polymer self-propagatingwaveguides.

In another embodiment, the three-dimensional open-cellular carbonmicro-truss structure template may be coated by a material selected fromthe group consisting of refractory metals, ceramics, silicon carbide,silicon nitride, hafnium carbide, chromium carbide, boron nitride, boroncarbide, aluminum oxide, titanium diboride, titanium nitride, zirconiumdioxide, titanium carbide, titanium carbonitride, tantalum carbide andtantalum nitride.

In yet another embodiment, the ordered diamond micro-truss may includebi-layer walls of diamond and a material. In some embodiments, thematerial is selected from the group consisting of refractory metals,ceramics, silicon carbide, silicon nitride, hafnium carbide, chromiumcarbide, boron nitride, boron carbide, aluminum oxide, titaniumdiboride, titanium nitride, zirconium dioxide, titanium carbide,titanium carbonitride, tantalum carbide and tantalum nitride.

In a further embodiment, a method of forming a diamond sandwich panelstructure is provided. The method includes providing a duct mold;depositing diamond on the internal portion of the duct mold to formdiamond face sheets; placing a coated micro-truss composite corestructure between the diamond face sheets; depositing diamond on themicro-truss composite core structure and mold to form a coatedmicro-truss composite core structure; etching the coated micro-trusscomposite core structure with an effective etchant to etch the coatedmicro-truss composite core; and removing the duct mold. In someembodiment the etching and removing occur simultaneously.

In one embodiment, a method of forming an ordered three-dimensionalopen-cellular diamond microtruss structure is provided which includesproviding an open-cellular polymer template and depositing a diamondcompatible coating directly on the open-cellular polymer template. Thisembodiment further includes removing the open-cellular polymer templateand depositing a diamond comprising material on the diamond compatiblecoating.

In some embodiments depositing the diamond compatible coating compriseselectroplating the open-cellular polymer template.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with reference to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 is a simplified flowchart illustrating a possible implementationfor forming an ordered three-dimensional open cellular diamondmicro-truss structure.

FIG. 2 illustrates an example structure of a three-dimensionalopen-cellular micro-truss structure.

FIGS. 3A-D are simplified cut away cross section illustrations along the3A-3A line of FIG. 2 illustrating various implementations for formingthree dimensional ordered diamond cellular structures.

FIGS. 4A-E are simplified illustrations showing a possibleimplementation for forming a three dimensional ordered diamond cellularstructure sandwich panel in accordance with an embodiment of theinvention.

FIG. 5 is a simplified flowchart illustrating a possible implementationfor forming an ordered three-dimensional open cellular diamondmicro-truss structure.

DESCRIPTION

Referring to FIG. 1, according to one implementation of the presentinvention, a method for forming an ordered three-dimensionalopen-cellular diamond micro-truss structure is provided. This methodinvolves providing an open-cellular polymer template 100; converting thepolymer template to an open-cellular carbon micro-truss structuretemplate 110; applying a diamond-compatible coating to the open-cellularcarbon micro-truss structure template with a material to form a coatedopen-cellular carbon micro-truss template 120; depositing a film havingdiamond on the coated open-cellular micro-truss template to form acoated micro-truss-diamond composite structure 130; and etching thecoated micro-truss diamond composite structure with an effective etchantunder conditions to etch the diamond-compatible coating from the coatedmicro-truss diamond composite structure, to create an orderedthree-dimensional open-cellular diamond micro-truss structure 140.

FIG. 2 illustrates an exemplary structure of a three-dimensionalopen-cellular micro-truss structure, which is used as athree-dimensional open-cellular polymer template structure in variousembodiments of the present invention. In context of embodiments of thepresent invention, an ordered three-dimensional open-cellular diamondmicro-truss structure is referred to as an ordered 3D structure at themicrometer scale.

The open-cellular polymer template 200 of FIG. 1 can be made using thepolymers described Ser. No. 11/580,335, filed on Oct. 13, 2006 entitledOPTICALLY ORIENTED THREE-DIMENSIONAL POLYMER MICROSTRUCTURES, byJacobsen, issued as U.S. Pat. No. 7,382,959 on Jun. 3, 2008, the entirecontents of which are incorporated herein by reference. Referring toFIG. 2, this open-cellular polymer template 200, is an orderedthree-dimensional polymer micro-truss structure is a self-supportingstructure, and is utilized to determine the final shape and dimensionsof the ordered three-dimensional open-cellular diamond micro-trussstructure.

Typically, the open-cellular polymer template 200 is a near net-shapedpolymer template created from an interconnected pattern ofself-propagating waveguides as described in the above referenced U.S.Pat. No. 7,382,959. The three-dimensional polymer template 200 includesat least three sets of self-propagating polymer waveguides extendingalong at least three respective directions. The at least three sets ofpolymer waveguides interpenetrate each other at a plurality of nodes toform a self-supporting structure having a plurality of orderedinterconnected pores. The polymer waveguides typically are fabricated byphotopolymerization, suitable for the construction of three dimensionalopen cellular polymer structures.

Turning to FIGS. 3A-D, shown are illustrations of an exampleimplementation of a process for forming various embodiments of a diamondmicro-truss structure. FIGS. 3A-D are simplified cut away cross sectionillustrations taken along the 3A-3A line of FIG. 2. FIG. 3A shows asimplified, enlarged cut away cross section of the open-cellular polymertemplate 200 of FIG. 2, converted to an open-cellular polymer carbonmicro-truss structure template 305. In a possible implementation, theopen-cellular polymer carbon micro-truss structure template 305 may bemade as described in Ser. No. 11/870,379, filed Oct. 10, 2007, entitledORDERED OPEN-CELLULAR CARBON MICRO-TRUSS STRUCTURE AND METHOD OF MAKINGSAME, by Jacobsen, issued as U.S. Pat. No. 8,585,944 on Nov. 19, 2013,the entire contents of which are incorporated herein by reference. Inaccordance with one embodiment, the open-cellular carbon micro-trussstructure template 305 typically is a vitreous carbon template. Thevitreous carbon template 305 comprises a network of vitreous carbonrods.

Shown in FIG. 3A, a diamond-compatible coating 315 c is applied to theopen-cellular carbon micro-truss structure template 305 with a materialto form a coated open-cellular carbon micro-truss template 315. Possiblediamond-compatible coating materials can be used since these materialscan withstand the conditions of the diamond deposition process and havea coefficient of thermal expansion well matched to diamond. Thediamond-compatible coating can include refractory metals, ceramics, andother materials. The coating may be a material selected from the groupconsisting of refractory metals, ceramics, silicon carbide, siliconnitride, hafnium carbide, chromium carbide, boron nitride, boroncarbide, aluminum oxide, titanium diboride, titanium nitride, zirconiumdioxide, titanium carbide, titanium carbonitride, tantalum carbide andtantalum nitride. Typically, the coating is silicon carbide.

Depending on the material selected, the coating 315 c can be applied byslurry coating, heat-treatments, chemical vapor deposition (CVD),chemical vapor infiltration (CVI), plasma enhanced chemical vapordeposition (PECVD), microwave assisted chemical vapor deposition and/orother gas phase deposition technique known to those skilled in the art.

According to another embodiment of the present invention, when thevitreous carbon template 305 is coated with silicon carbide 315 c toform a silicon carbide template 315, typically, any gas phase depositiontechnique known to those skilled in the art can be used. The siliconcarbide coating 315 c can be applied by chemical vapor infiltration(CVI) according to Ser. No. 12/074,727, filed Mar. 5, 2008, entitledCERAMIC MICRO-TRUSS, by Adam F. Gross, Alan J. Jacobsen; and RobertCumberland, issued as U.S. Pat. No. 7,687,132 on Mar. 30, 2010, theentire contents of which are incorporated herein by reference.

In some embodiments, the vitreous carbon 305 c may be removed after thediamond compatible coating 315 c has been applied. The vitreous carbon305 c may be removed or etched by burning out the vitreous carbon 315 c,e.g. heating in the presence of oxygen or ashing. Such a process orsimilar process may be used to remove the entire carbon template 305including the underlying open-cellular polymer template 200 (FIG. 2). Ifthe vitreous carbon 305 c is to be removed by burning it out, thisshould be performed before the diamond coating 325 c (FIG. 3B) isapplied so that the burning process does not affect/remove the diamondcoating 325 c.

Shown in FIG. 3B, a film or coating of diamond 325 c is deposited on thecoated open-cellular micro-truss template 315 (FIG. 3A) to form a coatedmicro-truss-diamond composite structure 325. In accordance with variousimplementations, the film of diamond 325 c may be deposited by any gasphase deposition technique known to those skilled in the art, selectedfrom the group consisting of chemical vapor deposition (CVD), hot wirechemical vapor deposition (HWCVD), plasma enhanced chemical vapordeposition (PECVD) and microwave-assisted chemical vapor deposition. Byusing such chemical vapor depositions of diamond in an ordered cellularmaterial, the amount of diamond used can be minimized and large-scalediamond structures can be fabricated.

The use of an ordered open cellular material allows optical componentsto be made of diamond. Diamond typically has the highest specificstiffness of any material; however, bulk diamond can be expensive andnot available in large sizes. In an embodiment of the present invention,the diamond may be monocrystalline, polycrystalline, nanocrystalline, oramorphous. The use of an ordered open-cellular material allows theoptical components to be made of diamond. Typically, the diamondstructure is polycrystalline, since it is known to those skilled in theart that larger grains lead to higher thermal conductivity, which canlead to lowed thermal distortion.

In an embodiment of the present invention, a film of polycrystalline,nanocrystalline, or amorphous diamond can be deposited on the siliconcarbide template 315 (FIG. 3A) to form a silicon carbide-diamondcomposite structure 325 using hot wire chemical vapor deposition(HWCVD).

Referring to FIGS. 3A, 3B, and 3C, in some embodiments, the carbon 305 cmay be removed after the diamond compatible coating 315 c has beenapplied, and the diamond compatible coating 315 c optionally may beremoved to leave an ordered three-dimensional open-cellular diamondmicro-truss structure 335. The diamond compatible coating 315 c may beetched with an effective etchant, such as molten salt, under conditionsto etch the silicon carbide coating 315 c from the coated micro-trussdiamond composite structure 325, while leaving the orderedthree-dimensional open-cellular diamond micro-truss structure 335. Thetype of molten salt, the etch temperature, and the etch time is selectedby empirical means to completely etch the diamond compatible coating 315c, but minimized etching of the diamond layer 325 c.

Referring to FIGS. 3B and D, in other implementations, only the carbontemplate 305 may be removed leaving the silicon carbide coating 315 c tocreate an ordered bilayered three-dimensional open-cellular diamondmicro-truss structure 345. The bilayer may be comprised of an outerdiamond layer 325 c and an inner silicon carbide (or other diamondcompatible material) layer 315 c. In various embodiments the diamondlayer 325 c may have multiple diamond structure types, which may beun-doped and/or doped.

As such, the three-dimensional diamond micro-truss structure may includea network 335 of hollow tubes made of diamond as illustrated in FIG. 3C.The network 335 of hollow tubes may include bi-layer walls of diamond.The network of hollow tubes may further include silicon carbide. Thus,the network of diamond tubes may have a partially filled core. Inanother embodiment, the diamond tubes have completely filled cores.

The term “an effective etchant” is used herein, is an etchant that iscapable of partially etching or completely etching, a compound inquestion. The effective etchant may be molten salts used alone or incombination and can be selected from the group consisting of potassiumhydroxide (KOH), sodium hydroxide (NaOH), potassium nitrate (KNO₃),sodium oxide (Na₂O₂) and sodium nitrate (NaNO₃). Typically, the moltensalt is potassium hydroxide.

Thus, in some implementations, the method of FIG. 1 for forming theordered three-dimensional open cellular diamond micro-truss structure335 (FIG. 3C) is provided, which may include providing an open-cellularpolymer template 100 and converting the polymer template to an vitreouscarbon template 110. The method further includes applying a siliconcarbide coating to the vitreous carbon template to form a siliconcarbide template 120 and depositing a film of diamond on the siliconcarbide template to form a silicon carbide-diamond composite structure130. Further, optionally, the silicon carbide-diamond compositestructure may be etched with an effective etchant under conditions toetch the silicon carbide coating to create an ordered three-dimensionaldiamond micro-truss structure 140, as shown in FIG. 3C. In otherimplementations, the vitreous carbon structure template and/or thesilicon carbide structure template may remain intact.

Typically, the silicon carbide coating is etched out using moltenpotassium hydroxide (KOH). This method typically yields a lightweightmaterial consisting of network of hollow diamond tubes withinterconnected cores.

In yet another implementation of the present invention, the diamond canbe grown directly on vitreous carbon via chemical vapor infiltration,eliminating the step of applying a silicon carbide coating to thevitreous carbon template. Thus, referring to FIG. 5, an open-cellularpolymer template is provided 500 which is converted into andopen-cellular carbon microstructure template 510. A diamond comprisingmaterial is deposited on the open-cellular carbon microstructuretemplate 530. Optionally, the open-cellular carbon microstructuretemplate may be removed 540.

The three-dimensional open-cellular carbon micro-truss structuretemplate can be coated by a diamond-compatible coating material selectedfrom the group consisting of refractory metals, ceramics, siliconcarbide, silicon nitride, hafnium carbide, chromium carbide, boronnitride, boron carbide, aluminum oxide, titanium diboride, titaniumnitride, zirconium dioxide, titanium carbide, titanium carbonitride,tantalum carbide and tantalum nitride. Typically, the material issilicon carbide.

In some embodiments, the diamond compatible coating is depositeddirectly on the polymer micro-truss 200 (FIG. 2) and the polymer ischemically etched prior to diamond deposition. For example, the diamondcompatible coating could be an electroplated metal such as Ni, Cr, Cu,Co, etc., or an electroplated semiconductor such as Si, Ge, GaAs, GaP,InP, InAs, InSb, In2S3, PbS, CdTe, CdSe, ZnSe, ZnTe, ZnCdSe, CdZnTe,CdS, Cu2S, In2Se3, CuInSe2, HgCdTe, etc. Preferably, the electroplateddiamond compatible coating is Ni, Cr, Cu, or their alloys. The polymercould be chemically etched in 3M NaOH for 24 hours at 60 degreesCelcius. Thus, referring to FIG. 1, the open-cellular polymer templateis provided 100 and the diamond compatible material coating is applied120 directly onto the open-cellular polymer template. The open-cellularpolymer template is removed 125 and then a diamond comprising materialis deposited on the diamond compatible material at 130. Optionally, thediamond compatible material coating may be removed 140.

As discussed above, the ordered diamond micro-truss may include bilayerwalls of diamond and a material. The material may be selected from thegroup consisting of refractory metals, ceramics, silicon carbide,silicon nitride, hafnium carbide, chromium carbide, boron nitride, boroncarbide, aluminum oxide, titanium diboride, titanium nitride, zirconiumdioxide, titanium carbide, titanium carbonitride, tantalum carbide andtantalum nitride. Typically, the material is silicon carbide. Typically,the material 315 c is a diamond-compatible coating material which canwithstand the conditions of the diamond deposition process and have acoefficient of thermal expansion well matched to diamond 325 c.

According to yet other embodiments, the three-dimensional orderedpolymer template 200 could be converted to/covered with other materials,which would then serve as the diamond growth template. For example, thismay be accomplished by electroplating a diamond compatible coatingdirectly on the open-cellular polymer template 200 (FIG. 2), thenetching out the polymer template 200 (FIG. 2) in a dilute base solution(or burning out the polymer template). Alternatively, this may beaccomplished by forming an inverse mold of the polymer truss andremoving the polymer truss, and then casting (enhanced with highpressure, if desired) a molten metal into the original truss geometry.

Turning to FIGS. 4A-E, in yet another embodiment a diamond sandwichpanel 440 is provided as shown in FIG. 4E. FIGS. 4A-E show one possibleimplementation of a method for forming a diamond sandwich panel 440. Thepanel 440 may include two face sheets 442; and a core 444. The core 444is an ordered three-dimensional open-cellular diamond micro-trussstructure. The core 444 is disposed between the two face sheets 442. Theface sheets 442 may include diamond. The three-dimensional orderedcellular diamond micro-truss structure 444 may be formed from theinterconnected pattern of polymer self-propagating waveguides 200 (FIG.2).

The method shown in FIGS. 4A-E includes providing a duct mold 400 anddepositing diamond 410 on the internal walls 400 w of the duct mold 400to form diamond face sheets 442, shown in FIG. 4A. The implementation ofFIGS. 4A-E further includes placing a coated micro-truss composite corestructure 415 between the diamond face sheets 442 as shown in FIG. 4B.The micro-truss composite core structure 415 may be a carbon template305 or a coated template 315 as discussed above with reference to FIGS.3A & 3B, or other template.

Shown in FIG. 4C, the implementation further includes depositing diamondon the micro-truss composite core structure 415 and mold 400 to form acoated micro-truss composite core structure 420.

In some implementations, the coated micro-truss composite core structure415 may be placed into the duct mold 400 prior to forming the facesheets 442 so that one or more face sheets may then be formed whendepositing diamond on the micro-truss composite core structure 415 andmold 400 to form a diamond coated micro-truss composite core structure420 within the duct mold 400 as shown in FIG. 4C.

Shown in FIG. 4D, the implementation further includes etching the coatedmicro-truss composite core structure 420 (FIG. 4C) with an effectiveetchant under conditions to etch the coating from the coated micro-trusscomposite core 415 (FIG. 4B). The duct mold 400 is removed as shown inFIG. 4E. The etching and removing can occur simultaneously in someimplementations.

The coated micro-truss composite core structure 415 may be formed asdescribed above, from an interconnected pattern of self-propagatingwaveguides as described in Ser. No. 11/580,335, filed on Oct. 13, 2006entitled OPTICALLY ORIENTED THREE-DIMENSIONAL POLYMER MICROSTRUCTURES,by Jacobsen, issued as U.S. Pat. No. 7,382,959 on Jun. 3, 2008.

The coated micro-truss composite core structure 415 may have a coatingmade from a material selected from the group consisting of refractorymetals, ceramics, silicon carbide, silicon nitride, hafnium carbide,chromium carbide, boron nitride, boron carbide, aluminum oxide, titaniumdiboride, titanium nitride, zirconium dioxide, titanium carbide,titanium carbonitride, tantalum carbide and tantalum nitride. Typically,the material is silicon carbide. The coated micro-truss composite corestructure comprises any material known to those skilled in the art,which can withstand the conditions of the diamond deposition process anda coefficient of thermal expansion well matched to diamond.

Thus, in some embodiments, a silicon carbide micro-truss 415 can beplaced inside the diamond 410 deposited in the mold 400.

Typically, the film of diamond is deposited by a gas phase depositiontechnique selected from one of chemical vapor deposition (CVD), hot wirechemical vapor deposition (HWCVD), plasma enhanced chemical vapordeposition (PECVD) and microwave-assisted chemical vapor deposition.

The diamond may be monocrystalline, polycrystalline, nanocrystalline, oramorphous. Typically, the diamond is polycrystalline.

After depositing diamond on the micro-truss composite core structure 444and mold 400, a diamond saw can be used to slice off the sides andexpose the micro-truss composite core 420 for etching. The coatedmicro-truss composite core structure 420 may be etched with an effectiveetchant, such as molten salt, under conditions to etch the coating fromthe coated micro-truss composite core. Some examples of the molten saltscan potassium hydroxide (KOH), sodium hydroxide (NaOH), potassiumnitrate (KNO₃), sodium oxide (Na₂O₂) and sodium nitrate (NaNO₃) andmixtures thereof. Typically, the molten salt is potassium hydroxide.

In some implementations, removing the duct mold 400 and etching thecomposite core structure 420, can occur simultaneously, depending on thematerials.

In some embodiments, etching of micro-truss composite core structure 420can be omitted, yielding a micro-truss-diamond composite structure.

In yet another embodiment of the present invention, doped diamond filmscan be used to control the electrical conductivity of the resultingstructure.

In yet another embodiment of the present invention, the face sheets canbe of a material other than diamond.

In another embodiment of the present invention, the manufacturingprocess can involve other methods of assembling a sandwich structure.The micro-truss core and face sheets could be fabricated separately andbrought together in a final assembly step. Multiple micro-trusses withdifferent geometries could be incorporated into a single sandwich panelcore.

In yet another embodiment of the present invention the material in thesandwich panel core could be a random open cell diamond foam.

Additional embodiments include, a composite structure in which thediamond micro-truss open cellular space can be filled with anothermaterial, for example, a high tensile-strength polymer. The opencellular space can be filled either partially or completely. Thecomposite structure in which the diamond micro-truss strut cores arefilled either partially or completely, with another material.

Furthermore, the various implementations and embodiments discussedherein are suited for making further articles and devices. Devices madefrom ordered three-dimensional open-cellular diamond micro-trussstructure have many applications and distinct advantages in many areas.Various embodiments of the present invention are well suited anddirected toward high strength structures that are very lightweight,which may be able to reduce the areal density of space optics, whilepreserving or increasing the stiffness. By using the superior qualitiesof diamond, various embodiments of this invention could enable newultra-lightweight high performance space optics and larger spacestructures.

In various embodiments, these diamond materials with 3-D orderedmicro-truss structures have applications that include but is not limitedto, lightweight structural materials (including sandwich panels), energyabsorbing materials, heat transfer applications (including heatspreaders, heat pipes, heat exchangers; high-temperature applicationssuch as certain heat pipes and solar thermal power generation whichutilize a molten salt as the heat transfer medium), sporting goodsequipment (for example, baseball bats, golf clubs, skis), windmillblades (stronger and lighter weight materials enable longer windmillblades which increases power output), prostheses and prosthetic limbs,implants for joint and bone replacement (using exact micro-trussstructure to tailor the stiffness to match bone), catalyst support,filtration/separation (especially of highly reactive materials,including molten salts), biological growth templates, flexible bodyarmor/reactive armor, electrical interconnects, wicking materials,functionally graded structures, batteries and fuel cells, deployablestructures (space structures), damping structures lightweight armor andspace optics (beryllium replacement).

The various previously described embodiments have many advantages. Byutilizing the superior properties of diamond, these advantages mayinclude providing diamond materials with ordered interconnectedthree-dimensional micro-truss structures that are ultra-lightweight,highly durable, hard materials, which can withstand a high temperature,oxidizing environment. Further, these free-standing ordered diamondmicro-truss structures would use the minimum amount of diamond so thatlarge-scale diamond structures can be fabricated. In particular, byconversion of scalable, net-shape, mechanically-efficientmicro-architected truss structures to these structures with diamond,various embodiments offer a number of advantages in comparison toconventional random foam structures (where performance typically may notbe optimized). In addition, the versatility, the cost effectiveness, andthe applications for use in aerospace optics, make various structuresand methods of embodiments of the invention especially valuable.Further, by using diamond to replace beryllium, safer workplaceenvironments would be available, which could reduce associatedprecautionary costs.

It is worthy to note that any reference to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment may beincluded in an embodiment, if desired. The appearances of the phrase “inone embodiment” in various places in the specification are notnecessarily all referring to the same embodiment.

The illustrations and examples provided herein are for explanatorypurposes and are not intended to limit the scope of the appended claims.This disclosure is to be considered an exemplification of the principlesof the invention and is not intended to limit the spirit and scope ofthe invention and/or claims of the embodiment illustrated.

Those skilled in the art will make modifications to the invention forparticular applications of the invention.

The discussion included in this patent is intended to serve as a basicdescription. The reader should be aware that the specific discussion maynot explicitly describe all embodiments possible and alternatives areimplicit. Also, this discussion may not fully explain the generic natureof the invention and may not explicitly show how each feature or elementcan actually be representative or equivalent elements. Again, these areimplicitly included in this disclosure. Where the invention is describedin device-oriented terminology, each element of the device implicitlyperforms a function. It should also be understood that a variety ofchanges may be made without departing from the essence of the invention.Such changes are also implicitly included in the description. Thesechanges still fall within the scope of this invention.

Further, each of the various elements of the invention and claims mayalso be achieved in a variety of manners. This disclosure should beunderstood to encompass each such variation, be it a variation of anyapparatus embodiment, a method embodiment, or even merely a variation ofany element of these. Particularly, it should be understood that as thedisclosure relates to elements of the invention, the words for eachelement may be expressed by equivalent apparatus terms even if only thefunction or result is the same. Such equivalent, broader, or even moregeneric terms should be considered to be encompassed in the descriptionof each element or action. Such terms can be substituted where desiredto make explicit the implicitly broad coverage to which this inventionis entitled. It should be understood that all actions may be expressedas a means for taking that action or as an element which causes thataction. Similarly, each physical element disclosed should be understoodto encompass a disclosure of the action which that physical elementfacilitates. Such changes and alternative terms are to be understood tobe explicitly included in the description.

While the present invention has been described in connection withcertain exemplary embodiments, it is to be understood that the inventionis not limited to the disclosed embodiments, on the contrary, it isintended to cover various modifications and equivalent arrangementsincluded within the spirit and scope of the appended claims, andequivalents thereof.

What is claimed is:
 1. A method of forming an ordered three-dimensionalopen-cellular diamond micro-truss structure, comprising: providing anopen-cellular polymer template comprised of an interconnected orderednetwork of interpenetrating micro-truss comprised of self-propagatingpolymer waveguides; converting the open-cellular polymer template to anopen-cellular carbon micro-truss template; and depositing a diamondcomprising film over the open-cellular carbon micro-truss template toform a coated micro-truss diamond composite structure; and etching themicro-truss diamond composite structure to form a network of hollowtubes comprised of diamond.
 2. The method of claim 1, wherein convertingthe open-cellular polymer template comprises converting to anopen-cellular carbon micro-truss structure template comprising avitreous carbon.
 3. The method of claim 1 further comprising applying adiamond-compatible coating comprising a diamond compatible material tothe open-cellular carbon micro-truss structure template to form a coatedopen-cellular carbon micro-truss template, and wherein depositing thediamond comprising film over the open-cellular carbon micro-trusstemplate comprises depositing the diamond comprising film onto thediamond-compatible coating.
 4. The method of claim 1, wherein theordered network comprises a plurality of first self-propagating polymerwaveguides extending along a first direction, a plurality of secondself-propagating polymer waveguides extending along a second direction,and a plurality of third self-propagating polymer waveguides extendingalong a third direction, wherein the first, second, and thirdself-propagating polymer waveguides interpenetrate each other at aplurality of nodes to form a continuous material.
 5. A method of formingan ordered three-dimensional open cellular diamond micro-trussstructure, comprising: providing an open-cellular polymer micro-trusstemplate comprised of an interconnected ordered network ofinterpenetrating micro-truss comprised of self-propagating polymerwaveguides; converting the open-cellular polymer microtruss template toan vitreous carbon template; applying a silicon carbide coating to thevitreous carbon template to form a silicon carbide template; removingthe vitreous carbon template; depositing a diamond comprising film onthe silicon carbide template to form a silicon carbide-diamond compositestructure; etching the silicon carbide coating to create an orderedthree-dimensional diamond micro-truss structure; and wherein etching thesilicon carbide coating comprises etching with molten potassiumhydroxide.
 6. The method of claim 5, wherein the ordered networkcomprises a plurality of first self-propagating polymer waveguidesextending along a first direction, a plurality of secondself-propagating polymer waveguides extending along a second direction,and a plurality of third self-propagating polymer waveguides extendingalong a third direction, wherein the first, second, and thirdself-propagating polymer waveguides interpenetrate each other at aplurality of nodes to form a continuous material.
 7. A method of formingan ordered three-dimensional open-cellular diamond microtruss structure,comprising: providing an open-cellular polymer template comprised of aninterconnected ordered network of interpenetrating micro-truss comprisedof self-propagating polymer waveguides; depositing a diamond compatiblecoating directly on the open-cellular polymer template; removing theopen-cellular polymer template; and depositing a diamond comprisingmaterial on the diamond compatible coating; and wherein removing theopen-cellular polymer template comprises etching the open-cellularpolymer template so as to form a network of hollow tubes comprised ofthe diamond.
 8. The method of claim 7, wherein depositing the diamondcompatible coating comprises electroplating the open-cellular polymertemplate.
 9. The method of claim 7, wherein removing compriseschemically etching the open-cellular polymer template.
 10. The method ofclaim 7, comprising removing the open-cellular polymer template prior todepositing the diamond comprising material.
 11. The method of claim 7further comprising removing the diamond compatible coating afterdepositing the diamond comprising material.
 12. The method of claim 7,wherein the ordered network comprises a plurality of firstself-propagating polymer waveguides extending along a first direction, aplurality of second self-propagating polymer waveguides extending alonga second direction, and a plurality of third self-propagating polymerwaveguides extending along a third direction, wherein the first, second,and third self-propagating polymer waveguides interpenetrate each otherat a plurality of nodes to form a continuous material.
 13. A method offorming an ordered three-dimensional open cellular diamond micro-trussstructure, comprising: providing an open-cellular polymer micro-trusstemplate comprised of an interconnected ordered network ofinterpenetrating micro-truss comprised of self-propagating polymerwaveguides; converting the open-cellular polymer micro-truss template toa vitreous carbon template; applying a silicon carbide coating to thevitreous carbon template to form a silicon carbide template; removingthe vitreous carbon template; depositing a diamond comprising film onthe silicon carbide template to form a silicon carbide-diamond compositestructure; etching the silicon carbide coating to create an orderedthree-dimensional diamond micro-truss structure; wherein depositing adiamond comprising film comprises depositing at least one ofmonocrystalline, polycrystalline, nanocrystalline, or amorphous diamondby hot wire chemical vapor deposition; and wherein etching the siliconcarbide coating comprises etching with molten potassium hydroxide. 14.The method of claim 13, wherein the ordered network comprises aplurality of first self-propagating polymer waveguides extending along afirst direction, a plurality of second self-propagating polymerwaveguides extending along a second direction, and a plurality of thirdself-propagating polymer waveguides extending along a third direction,wherein the first, second, and third self-propagating polymer waveguidesinterpenetrate each other at a plurality of nodes to form a continuousmaterial.